external function framework needs ef_get_axis_calendar utility routine

[karlmsmith]

Reported by @AnsleyManke on 9 May 2006 18:42 UTC
We have a function ef_get_axis_info which returns

axname, ax_units, backward, modulo, regular

But we need to be able to get at the calendar-axis name and perhaps other things
like the days-per-month, which is stored internally in cals_days_in_month.

Migrated-From: http://dunkel.pmel.noaa.gov/trac/ferret/ticket/1411